1. Field of the Invention
The present invention relates to a magnetic guiding apparatus for exposure apparatus utilized in manufacturing devices, such as semiconductor devices, liquid-crystal display devices, and the like, and inspection apparatus, or the like, in which a stage mounting an original plate, such as a mask, a reticle, or the like, or a substrate to be exposed or inspected, such as a semiconductor wafer, a glass substrate, or the like, is moved by a magnetic guide.
2. Description of the Related Art
An exposure apparatus utilized in a process for manufacturing devices, such as semiconductor devices, liquid-crystal display devices, or the like, has stage apparatus for moving a substrate to be exposed, for example, an original plate, such as a mask, a reticle, or the like, or a substrate to be exposed, such as a semiconductor wafer, a glass substrate, or the like.
Such a stage apparatus is disclosed, for example, in Japanese Patent Publication No. 3145355. In this stage device, a Y stage is guided by a yaw guide and is mounted on a stage surface plate. An air pad is provided between the Y stage, and the stage surface plate and the yaw guide.
An X slider is provided so as to surround a Y slider connected to the Y stage. An air pad is provided between a side of the Y slider and a side of the X slider. An air pad is also provided between the X slider and the stage surface plate. According to such a structure, since the Y slider is slidable in the y direction and the X slider is slidable with respect to the Y slider in the x direction, the X slider is slidable both in the x and y directions.
A magnetic guiding apparatus using an electromagnet is disclosed, for example, in Japanese Patent Application Laid-Open (Kokai) No. 04-245406 (1992). A method for removing remanence is disclosed, for example, in Japanese Patent Application Laid-Open (Kokai) No. 09-068221 (1997), which discloses AC demagnetization in which demagnetization is performed by causing an AC current to flow in an electromagnet and gradually reducing the magnitude of the current from a maximum current to zero.
In the stage described in Japanese Patent Publication No. 3145355, transmission of a force by an air pad is only about 1 kgf/cm2 as a value converted into pressure. Accordingly, it is estimated that when, for example, a force to be transmitted to the X slider increases by adding a fine-movement stage, the value of the force exceeds the capability of force transmission by the air pad.
If the air pad is replaced by a rolling guide, the problems of a short life and dust arise, particularly, in an apparatus in which long-time continuous operation and a high-degree of cleanness are required, such as in an exposure apparatus.
In order to solve the above-described problems, an approach of utilizing a magnetic guide using an electromagnet disclosed in Japanese Patent Application Laid-Open (Kokai) No. 04-245406 (1992) instead of the air pad disclosed in Japanese Patent Publication No. 3145355 may be adopted. This configuration can improve the force transmission capability. Furthermore, since silicon steel having little magnetic hysteresis can be used as the material for the electromagnet and the target, the electromagnet and the target are hardly magnetized under ordinary control conditions.
However, in runaway of the electromagnet caused by an unintended accident, an excessive magnetic flux may pass through the target, resulting in an increase of remanence. The runaway of the electromagnet indicates a case in which a desired servo is not applied to the stage. This happens, for example, when a current driver fails, or when a large current passes through a driving coil for the electromagnet caused by a software bug, or the like. The generated remanence operates as a disturbance for an X-slider control system, resulting in degradation in the accuracy of subsequent positioning.
A method for solving the problem of remanence is disclosed, for example, in Japanese Patent Application Laid-Open (Kokai) No. 09-068221 (1997). However, in a stage apparatus, since the positional relationship between the electromagnet and the target is movable, the position of a magnetic flux at the target is unknown, thereby causing a problem in efficiency if demagnetization is performed over the entire region of the target.